CONSERVATION TILLAGE METHODS

FOR CABBAGE PRODUCTION

by

Velva Ann Love

Thesis submitted to the Faculty of the

Virginia Polytechnic Institute and State University

in partial fulfillment of the requirements for the degree of

Master of Science

M. M. Alley

1Il

Horticulture

APPROVED:

R. D. Morse, Chairman

December 10, 1986

Blacksburg, Virginia

C.R. O'Dell

CONSERVATION TILLAGE METHODS

FOR CABBAGE PRODUCTION

by

Velva Ann Love

R. D. Morse, Chairman

Horticulture

(ABSTRACT)

Cabbage ( Brassica oleracea L.) production in Virginia is concentrated in the mountainous

southwest region of the state where soil erosion and soil-moisture deficits are major problems as-

sociated with row-crop agriculture. The objectives of this study were to assess the applicability of

conservation tillage systems for cabbage production. Four tillage systems (conventional tillage, CT;

no-tillage, NT; and two types of strip tillage - Ro-till, RT, and chisel plow, CP) and three planting

dates (early, mid and late) were compared in 1985 and 1986. Plants were set with a locally adapted

no-till transplanter into a cover crop of cereal rye (Secale cereale L.). Under unusually rainy con-

ditions in 1985, cabbage yields with NT were lower than with CT; while with dry weather prevailing

in 1986, NT and CT yields were equal for all planting dates. Yields in strip tillage systems were

equal or higher than NT and CT with ample or deficit soil moisture. RT out-yielded both CT and

NT in 1986. Yield was positively correlated with soil moisture content in 1986, but not in 1985.

Once-over resetting was done in all plots resulting in no differences in plant numbers among tillage

treatments. Head size was affected by tillage systems and was highly correlated with yield. These

data indicate that (i) conservation tillage systems are viable alternatives to CT for production of

cabbage, and (ii) available water resources and soil drainage should be important considerations in

selection of the most productive tillage system.

DEDICATION

I would like to dedicate this thesis to Mom, Dad, Kenner Phipps, Sarah Kay and Gordon.

DEDICATION iii

Acknowledgements

Acknowledgements

Sincere appreciation goes to my committee - Dr. Ronald Morse, Dr. Mark Alley and Mr.

Charles O'Dell for all of their help and support in preparing my thesis. A special thanks goes to

the grad students, technicians and farm crew for their assistance with planting, hoeing and harvest-

ing my cabbage; to Buddy and Donnie for their expert groundhog control; to Michele and Debbie

for making my computer work possible; to the horticulture faculty and staff for all of their help and

encouragement; and especially to Mom and Dad for helping me through school and being there in

the cabbage patch with me.

Acknowledgements iv

Table of Contents

Il\l'"fRODUCTION . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . I

LITERATURE REVIEW . . . . • . . . . . . . . . . . . • . . . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . 3

LITERATURE CITED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

MATERIALS AND l\1ETHODS ........................................... 15

Spring, Summer 1985 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Spring, Summer 1986 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

RESULTS AND DISCUSSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

LITERATURE CITED . . . . . . . . . . . . . . . . . . . . • . • . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

APPENDIX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . . 30

Table of Contents V

Vita 35

Table of Contents vi

List of Tables

Table 1. Effect of tillage method on vegetable crop yield. . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Table 2. Dry matter yield of rye cover crop (MT/ha). . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Table 3. Influence of tillage systems on head number, yield and size of cabbage. . . . . . . . . 22

Table 4. Effects of planting dates and tillage systems on soil temperature and soil moisture content ...................................................... 24

Table 5. Monthly and annual precipitation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Table 6. Individual effects of planting date and tillage system on head number, yield and size of cabbage in 1985. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Table 7. Individual effects of planting dates and tillage systems on head number, yield and head size of cabbage in 1986. . ..................................... 32

Table 8. Influence of planting date on head number, size and yield of cabbage. . . . . . . . . . 33

Table 9. Influence of planting dates on soil moisture and soil temperature. . . . . . . . . . . . . 34

List of Tables vii

INTRODUCTION

Vegetable growers are becoming more interested in tillage methods that decrease erosion and

increase water infiltration and soil moisture retention while maintaining or increasing marketable

yields. As a result, experiments testing conservation tillage systems for vegetables have been con-

ducted by several researchers (6, 21, 22, 24, 28, 31). No-tillage (NT) vegetable yields have not al-

ways been as good or better when compared to conventional tillage yields. Beste ( 6) reported no

yield differences between NT and conventional tillage (CT) for tomatoes and lima beans; however,

CT cucumbers outyielded NT. Knavel et al. (21) observed reduced yields under NT for cucumbers,

tomatoes, and peppers and no differences for sweet com. NT yields were lower than CT because

of reduced plant stands and in some cases, lower yields per plant. Morse et al. (31) found higher

yields for cabbage, cucumbers, squash, and tomatoes under NT than CT. The increased NT yields

were attributed to improvements in soil moisture resulting in increased fruit number per plant rather

than average fruit size of the fruiting vegetables. Head size accounted for the increased NT yields

with cabbage.

Cabbage in Southwest Virginia is primarily grown on steep slopes where erosion is a major

problem (25). An estimated 90 MT/ha of topsoil is lost from land in CT cabbage production in

Carroll County each year; however, soil loss often exceeds 180 MT/ha (25). Water deficits are also

a problem because of low water infiltration rates. Irrigation is not regularly practiced because of

INTRODUCTION

the lack of proximity to water sources. Conservation tillage which reduces soil erosion and gener-

ally increases soil moisture would appear to be a reasonable alternative for cabbage production on

steep slopes (5, 7, 8, 17, 19, 22).

Conservation tillage is any tillage and planting system that retains at least 30% residue cover

on the soil surface after planting and includes no-till, ridge-till, mulch-till, strip-till and other re-

duced tillage and planting systems (1). Residue cover may be from meadow, winter cover crop,

small grain or row crops (1). No-tillage tends to decrease soil temperature which can lead to poor

germination and slow early development of many spring-planted crops (5, 18, 39). Cold, wet soil,

especially silts and clays, tends to be less friable under NT systems and when field setting trans-

plants, results in poor soil-root contact (14) .. Under such conditions with NT, crop growth and

potential yield may be reduced compared to CT and possibly strip tillage (ST). Strip tillage is a

compromise between conventional and no-tillage which combines benefits of both systems (24, 36,

38). Strip tillage is practiced with varying degrees of soil disturbance and width of the tilled areas.

In-row tillage may be accomplished with a rototiller, chisel plow, coulters, row cleaners, etc. (1, 12,

36).

The objectives of this study were to assess the effects of tillage systems and the interaction

of planting dates X tillage systems on yield of non-irrigated cabbage.

INTRODUCTION 2

LITERATURE REVIEW

Data on conservation tillage production of vegetables are limited. However, extensive re-

search has been performed on reduced tillage of agronomic crops; therefore, this review primarily

reflects that research.

NUTRIENT AVAILABILITY. No-tillage (NT) agriculture eliminates plowing, thus fertilizer

is not incorporated into the soil. With NT, fertilizer is either broadcast, banded or knifed into the

soil thus altering the nutrient content in the soil layers compared to conventionally tilled (CT) soils,

however, nutrient availability under reduced tillage systems has been shown to be generally ade-

quate for crop growth.

NITROGEN. Nitrogen is often the most limiting nutrient in NT crop production because

it is readily lost from the soil through volatilization, denitrification, or leaching (16, 21, 52). Hoeft

and Randall ( 16) report that nitrogen levels are related to microbial activity which in tum is influ-

enced by soil temperature, moisture and compaction. Surface residue on NT soils increases soil

moisture content and decreases soil temperature, which in turn decreases aerobic and increases

anaerobic microbial populations. With fewer aerobic microbes, nitrogen mineralization is decreased

and nitrogen availability is reduced.

Valiulis (52) cites two conditions with NT that favor nitrogen loss from the soil. First, en-

hanced soil moisture content increases leaching of nitrogen. Second, soil surface residues increase

LITERATURE REVIEW 3

the organic matter content which in turn increases urease activity and subsequent ammorna

volatilization from surface applied urea.

PHOSPHORUS. Phosphorus is immobile in the soil; therefore, fertilizer phosphorus is

generally found in the top 5-10 cm of soil under NT systems ( 16, 32, 33, 45, 52). In an eleven year

continuous study, Moschler et al. (32) found phosphorus levels to be higher under NT in the 0-20

cm soil layer than under CT; however, in the 20-40 cm layer NT and CT had equal phosphorus

content. Shear and Moschler (45) reported that total available phosphorus levels were 75% higher

under NT than under CT in the 0-20 cm soil layer. Concentration of phosphorus in the upper layer

of soil corresponds with the area of soil moisture which allows adequate phosphorus uptake under

NT soils and equal or better yields over CT (16, 52).

POTASSIUM. Potassium is slightly mobile and becomes stratified like phosphorus with

NT broadcast fertilization (16, 52). Hoeft and Randall (16) found decreased potassium uptake

under NT when the soil was abnormally dry and when soil had poor aeration due to compaction.

Triplett (49) concluded that potassium nutrition is adequate under NT with broadcast fertilization.

Adequate soil moisture near the surface that allows root proliferation is necessary for potassium and

phosphorus fertilizer uptake (52).

SOIL pH. Broadcast application of nitrogen fertilizers with NT causes the pH to decrease in

the top 3-8 cm of soil over a period of time ( 16, 45, 52). Hoeft and Randall ( 16) pointed out that

soil pH changes depend on nitrogen rate and placement along with soil type. Acid conditions in

the top soil layer decrease the effectiveness of some herbicides, especially the triazine herbicides, and

may inhibit root growth (16, 52). Broadcast application of lime may become necessary on con-

tinuous NT fields. Valiulis (52) recommends using half the rate of lime recommended for CT ap-

plied twice as often. In some cases, liming has also improved yields ( 45).

SOIL PHYSICAL PROPERTIES. Tillage systems alter the physical properties of the soil.

Ketcheson (20) reported higher mechanical resistance under NT than CT. He concluded that

higher penetrometer readings corresponded with restricted root growth under NT. 1be restricted

root growth in tum prevented adequate soil moisture uptake which could not be overcome by ad-

ditional fertilization. Peterson (38) recorded higher bulk density and penetrometer readings under

LITERATURE REVIEW 4

NT than CT with intermediate values for chisel plow (CP). Knavel et al. (21) studying four dif-

ferent vegetable crops under NT also found higher penetrometer values under NT than CT. Shear

and Moschler ( 45) reported no differences in bulk densities between NT and CT after a 6 year

continuous com study. They concluded that soil compaction is no greater after several years of

NT than after CT.

EROSION CONTROL Conservation tillage has become a major factor in providing erosion

control on sloping farm land (3, 5, 15, 36, 38, 44). Peterson et al. (38) measured rill erosion and

found that NT and CP nearly eliminated soil loss while there was considerable loss under CT.

Angle et al. (3) compared NT and CT in a watershed runoff study. Although both treatments had

low rates of runoff, CT produced four times as much runoff as did NT. Suspended sediment loss

was eleven times greater under CT and soluble solids loss was significantly greater than NT. Al-

though yields may be decreased under NT, most farmers and researchers agree that maintaining a

plant cover on hilly terrain to decrease erosion more than offsets the loss in yield (5, 15).

SOIL TEMPERATURE. Soil temperatures are generally lower under reduced tillage than

under CT systems (5, 14, 18, 38, 39, 41, 46). Johnson and Lowery (18) reported lower soil tem-

peratures with NT during the early part of the growing season; however, by the end of June, the

difference was less than one degree C. No-tillage soils had the highest volumetric heat capacity,

CT the lowest, and CP intermediate; therefore, given equal profile heat inputs, NT and CP soils

will have lower temperatures than CT. Temperature finding were supported by Potter et al. (41)

and Peterson et al. (39) with NT < ST < CT.

In a NT tomato and cucumber study, Beste (6) reported the NT plots had slightly higher

temperatures at the 5 cm depth than CT plots. He attributed the higher temperatures to a short

rye-straw mulch which allowed sunlight to penetrate the soil surface and to reduced soil heat losses

by radiation from the soil surface. Also, the mulch helped decrease the cooling effect of the wind.

Radke et al. (43) found soil temperatures and soil structure under NT and CT to be similar due to

cool weather and rain. Peterson et al. (38) found no difference in soil temperature between CT and

strip tillage (ST); however, NT temperatures were 2-3 degrees Clower.

LITERATURE REVIEW s

Lower spring temperatures under NT and ST may explain poorer germination and lower

yields than under CT with early planting dates (5, 18, 39). Tessore et al. (46) report cooler soil

temperatures under NT to be an advantage in plantings of fall vegetable crops.

SOIL MOISTURE. Researchers have found NT soils to be higher in moisture content than

CT soils (5, 7, 8, 17, 19, 22, 30, 38, 43, 46). Several authors cited decreased evaporation from the

NT mulch cover as a major factor in increasing moisture reserves especially during the early part

of the growing season (5, 7, 8, 43). Blevins et al. (7) report high evaporation losses early in the

growing season. As the plants grow, the crop produces a shading effect which decreases evaporation

and transpiration becomes the major source of water depiction. Bond and Willis (8) reported lower

evaporative potentials under NT. Shaded soil combined with lower temperatures form a temper-

ature gradient causing the water to move from higher to lower temperature areas.

Surface residue increases water infiltration (44, 51). In a three year com study, Triplett ct al.

(51) found NT soil with 80% residue to have a greater infiltration rate and total infiltration than

did CT soils and NT soils with less residue cover. They attributed the increased infiltration to: l)

physical protection from rain drop impact afforded by the mulch; and 2) diff crence in structure and

stability generated over a three-year period under the mulch. After intense storms, NT with double

residue had the highest moisture recharge while NT with residues removed had the lowest recharge.

Low intensity storms created no differences in recharge among the treatments because rainfall rates

did not exceed infiltration rates.

Peterson et al. (38) compared rotations of winter wheat with crops under NT, CT, and ST.

They found no difference in soil moisture between treatments in dry years. In normal years, NT

had slightly higher moisture values during the first two months, but this difference disappeared as

the crop grew. There was no difference in moisture between conventional and chisel tillage.

Cover crops for NT plantings may deplete soil moisture supply before the crop is planted.

Hoyt ( 17) reports poor kill of rye cover crop to be a factor in removing water from the soil and

decreasing broccoli and cabbage yields. In a NT cabbage study, Knavel and Herron (23) reported

the effects of killing a Sudan grass cover crop at different heights. Grass allowed to grow 30 cm

LITERATURE REVIEW 6

high depleted soil moisture and reduced yields; however, killing the grass at 15 cm conserved soil

moisture.

WEED CONTROL. No-tillage crop production relies entirely on herbicides for effective weed

control (49). New herbicides are being labeled for use on vegetable crops; however, weed pressure

is still a major concern for NT farmers.

Herbicides must give initial and residual control on NT crops, and combinations of herbicides

are usually needed for satisfactory weed control (49). An effective, non-selective knock-down

herbicide applied before planting is an essential part of a weed control program (40). A pre-

emergence herbicide with low volatility is recommended (2). Length of herbicide activity is im-

portant especially when herbicides are applied several days prior to planting (50). Time and rate

of application is important in order to kill the weeds while they arc in the vulnerable seedling stage

(11, 27, 50). A residual herbicide with good solubility (2), and rain or irrigation soon after appli-

cation to move the herbicide into the soil is necessary to achieve effective season long weed control.

Lack of precipitation often leads to poor weed control ( 13, 26).

Stubble from cover crops on reduced tillage soils often intercepts and retains herbicides and

decreases the rate that reaches the soil, thus reducing their effectiveness ( 4, 13, 53, 54). Atrazinc

intercepted by stubble often volatilizes or degrades before reaching the soil (53). Williams and

Wicks ( 53) concluded that broadleaf weeds present at planting time often intercept foliar contact

herbicides which allows small underlying grass plants to survive and become a problem later. Other

reports also indicate greater grass weed numbers with NT and no difference between NT and CT

broadleaf populations (4, 54).

Moomaw and Burnside (26) concluded that greater moisture rather than herbicide retention

by the stubble caused weed pressure to be greater under NT. The increased moisture with NT al-

lowed weed seeds to germinate and grow while the CT soil was so dry the weed seeds did not

germinate.

Several researchers report problems with perennial weeds after several years of continuous

NT (50, 53, 54). The rhizomes are not disturbed so the weeds spread and become a problem.

LITERATURE REVIEW 7

VEGETABLE YIELD. No-tillage vegetable crop research has provided varied and incon-

clusive results among different researchers working with the same crop and between different crops.

Table 1 summarizes the findings of this review. Nine studies found no differences between

NT and CT; nine found higher yields under NT; and ten found higher yields with CT.

CABBAGE PRODUCTION. No-tillage cabbage production results comparing NT and CT

are varied. Knavel and Herron (22) obtained higher head weights and yields with CT than with

NT when planting early spring cabbage in March and April. Morse and Seward (29) planted

cabbage in June and July and found NT cabbage to have equal or better head weights and yields

than with CT.

Knavel and Herron (23) planted fall cabbage in August. Sudan grass mulch was cut at 15 cm

and 30 cm heights and compared to CT treatments. The grass cover in the 15 cm height soon dried

out and left little residue. Yield in the 15 cm height was equal to that of the CT plots. The grass

in the 30 cm plots depleted the soil moisture supply before planting and thus decreased head weight,

yield and number of marketable heads. They concluded that planting fall cabbage in NT Sudan

grass cover is of no benefit in terms of moisture conservation.

Knavel and Herron (22) reported greater nitrogen requirements for NT cabbage than CT es-

pecially at close spacings. Sidedressing nitrogen increased the NT head weight; however, CT still

had greater head weights. Peck (37) reported nitrogen uptake rates of cabbage to be low during the

seedling stage, high during rnidseason and moderate near harvest. Broadcasting or banding at

planting with an additional sidedressing of nitrogen increased yield, but decreased quality due to

burst heads and tip burn. He concluded that nitrogen uptake is continuous and depends on avail-

able soil and/or fertilizer nitrogen in the rhizosphere.

Drew ( 10) studied the effect of soil moisture on cabbage growth and concluded that the in-

crease in weight of cabbage heads is nearly proportional to the total amount of water applied. 1be

cabbage crops' last three weeks of development seems to be the most critical for irrigation because

added moisture during this period may overcome the effect of earlier dry soil conditions. He con-

cluded that the later the dry period, the more the yield was depressed. The moisture effect corre-

sponds to the cabbage growth habit. Cabbage grows slowly·in early life, taking from 90-100 days

LITERATURE REVIEW 8

Table I. Effect of tillage method on vegetable crop yield.

Table I. Effect of tillage method on vegetable crop yield~

Crop

Acom Squash

Asparagus

Broccoli

Cabbage

Carrots

Cucumber

Lima Beans

Pepper

Potato

Snap Beans

Sweet Com

Tomato

Y cllow Squash

Zucchini Squash

Yield

CT NT

... NS ... ... NS

NS +

NS +

...

+

:;-.;s

NS NS

NS +

NS + +

...

...

NS

NS +

NS

NS ...

NS

NS

NS I\S

NS

::\'S

+

+ +

+

Authors

Morse et al. (28)

Putnam (42)

Konslcr et al. (24) Morse ct al. (29)

Knavel ct al. (22) Konslcr ct al. (24) :Vlorse ct al. ( 29) Morse ct al (31)

Orzolck ct al. (35)

Beste ( 6) Knavel ct al. (21) Morse ct al. (31)

Beste ( 6) Mullins et al. (34)

Knavel ct al. (21)

Hoyt ( 17) Thornton ( 47)

Mullins ct al. (34) Tompkins ct al. ( 48)

Knavel ct al. (21) Peterson ct al. (39)

Beste ( 6) Doss ct al. (9) Kna•/cl ct al. (21) \.forsc ct al. (31)

Morse ct al. (31) Tcssorc ct al. ( 46)

Tcssorc ct al. ( 46)

"+ - significantly higher at the 5% L:·:cl; NS - no significance at the 5% lc\'cl.

LITEIL\TLHE HEVIE\V ()

to reach the grand period of growth. Then cabbage heads double in weight about every nine days

and require adequate water supplies to maintain turgor pressure.

LITERATURE REVIEW 10

LITERATURE CITED

I. Anon. 1984. 1983 National survey: conservation tillage practices, executive summary. Natl Assn. of Conservation Districts.

2. Anon. 1986. Conservation tillage can add up to fewer weeds and herbicides. Ciba-Geigy Seed Nwsl. Winter 1986: 1-2.

3. Angle, J. S., G. McClung, M. S. McIntosh, P. M. Thomas, and D. C. Wolf. 1984. Nutrient losses in runoff from conventional and no-till com watersheds. J. Env. Qual. 13(3):431-435.

4. Banks, P.A. 1986. Weed control and interference research. Proceedings of the Southern Region No-tillage Conference. Southern Reg. Ser. Bul. 319:50-51.

5. Bennett, 0. L., E. L. Mathias, and P. E. Lundberg. 1973. Crop responses to no-till management practices on hilly terrain. Agron. J. 65:488-49 I.

6. Beste, C. E. 1973. Evaluation of herbicides in no-till planted cucumbers, tomatoes, and lima beans. NE Weed Sci. Soc. Proc. 27:232-239.

7. Blevins, R. L., D. Cook, S. H. Phillips, and R. E. Phillips. 1971. Influence of no-tillage on soil moisture. Agron J. 63:593-596.

8. Bond, J. J. and W. 0. Willis. 1971. Soil water evaporation: long-term drying as influ-enced by surface residue and evaporation potential. Soil Sci. Soc. Amer. Proc. 35:984-987.

9. Doss, B. D., J. L. Turner, and C. E. Evans. 1981. Influence of tillage, nitrogen, and rye cover crop on growth and yield of tomatoes. J. Amer. Soc. Hort. Sci. 106(1):95-97.

10. Drew, D. H. 1966. Irrigation studies on summer cabbage. J. Hort. Sci. 41:103-114.

11. Erbach, D. C. and W. G. Lovely. 1975. Effect of plant residue on herbicide performance in no-tillage com. Weed Sci. 23(6):512-515.

12. Gergen, B. 1981. One-pass tillage tool. Farm Ind. News. May-June 1981 :60.

LITERATURE CITED 11

13. Ghadiri, H., P. J. Shea, and G. A. Wicks. 1984. Interception and retention of atrazine by wheat (Triticum aestivum L.) stubble. Weed Sci. 32:24-27.

14. Griffith, D. R., J. V. Mannering, H. M. Galloway, S. D. Parsons, and C. B. Richey. 1973. Effect of eight tillage-planting systems on soil temperature, percent stand, plant growth, and yield of corn on five Indiana soils. Agron. J. 65:321-326.

15. Hillyer, G. 1984. No-till know how. Soybean Dig. 44(4):16-18.

16. Hoeft, R. G. and G. W. Randall. 1985. Tillage affects fertility - how to alter one when you change the other. Crops and Soils Mag. 37(4):12-16.

17. Hoyt, G. D. 1985. Conservation tillage systems for vegetable production. Penn. Veg. Conf.:44-48. (Abstr.)

18. Johnson, M. D. and B. Lowery. 1985. Effect of three conservation tillage practices on soil temperature and thermal properties. Soil Sci. Soc. Am. J. 49:1547-1552.

19. Jones, J. N., Jr., J.E. Moody, and J. H. Lillard. 1969. Effects of tillage, no-tillage, and mulch on soil water and plant growth. Agron. J. 61:719-721.

20. Ketcheson, J. W. 1980. Effect of tillage on fertilizer requirements for corn on a silt loam soil. Agron J. 72:540-542.

21. Knavel, D. E., J. Ellis, and J. Morrison. 1977. The effects of tillage systems on the performance and elemental absorption by selected vegetable crops. J. Amer. Soc. Hort. Sci. 102(3):323-327.

22. Knavel, D. E. and J. W. Herron. 1981. Influence of tillage system, plant spacing, and nitrogen on head weight, yield, and nutrient concentration of spring cabbage. J. Amer. Soc. Hort. Sci. 106(5):540-545.

23. Knavel, D. E. and J. W. Herron. 1985. Effect of sudan grass on yield and elemental content of cabbage. HortScience. 204(4):680-681.

24. Konsler, T. R. and G.D. Hoyt. 1986. Response of broccoli and cabbage to winter cover residues and degree of tillage. (Unpub. data).

25. McGrady, H. 1983. Chairman, New River Soil and Water Conservation District. (Per-sonal Correspondence).

26. Moomaw, R. S. and 0. C. Burnside. 1979. Com residue management and weed control in close-drilled soybeans. Agron. J. 71 :78-80.

27. Moomaw, R. S. and A. R. Martin. 1978. Weed control in reduced tillage com pro-duction systems. Agron. J. 70:91-94.

28. Morse, R., B. McMaster, and C. Tessore. 1983. Increased squash yields with no-tillage mulch. The Veg. Growers News. 37(5):1.

29. Morse, R. D. and D. L. Seward. 1986. No-tillage production of broccoli and cabbage. Applied Agr. Res. 1(2):96-99.

30. Morse, R. D. and C. Tessore. 1984. Efficient water use: conservation of soil moisture with no-tillage. The V cg. Growers News. 39(3): 1 & 4.

LITERATURE CITED 12

31. Morse, R. D., C. M. Tessore, W. E. Chappell, and C.R. O'Dell. 1982. Use of no-tillage for summer vegetable production. The Veg. Growers News. 37(1):1.

32. Moschler, W. W., D. C. Martens, and G. M. Shear. 1975. Residual fertility in soil continuously field cropped to com by conventional tillage and no-tillage methods. Agron. J. 67:45-48.

33. Moschler, W. W. , G. M. Shear, D. C. Martens, G. D. Jones, and R. R. Wilmouth. 1972. Comparative yield and fertilizer efficiency of no- tillage and conventionally tilled com. Agron. J. 64:229-231.

34. Mullins, C. A., F. D. Tompkins, and W. L. Parks. 1980. Effects of tillage methods on soil nutrient distribution, plant nutrient absorption, stand, and yields of snap beans and lima beans. J. Amer. Soc. Hort. Sci. 105(4):591-593.

35. Orzolek, M. D. and R. B. Carroll. 1978. Yield and secondary root growth of carrots as influenced by tillage system, cultivation, and irrigation. J. Amer. Soc. Hort. Sci. 103(2):236-239.

36. Oschwald, W. R. 1973. Chisel plow and strip tillage systems. p.194-202. In: Soil Cons. Soc. Amer. Conservation Tillage: the proceedings of a national conference. Ankeny, Iowa.

37. Peck, N. H. 1981. Cabbage plant responses to nitrogen fertilization. Agron J. 73:679-684.

38. Peterson, C. L., E. A. Dowding, K. N. Hawley, and R. W. Harden. 1983. The chisel-planter minimum tillage system. Trans. of ASAE. 378-383.

39. Peterson, K. L., H. J. Mack, and D. E. Booster. 1986. Effect of tillage on sweet com development and yield. J. Amer. Soc. Hort. Sci. 111(1):39-42.

40. Pollard, F. and G. W. Cussans. 1981. The influence of tillage on the weed flora in a succession of winter cereal crops on a sandy loam soil. Weed Res. 21:185-190.

41. Potter, K. N., R. M. Cruse, and R. Horton. 1985. Division S-6-soil and water man-agement and conservation: tillage effects on soil thermal properties. Soil Sci. Soc. Am. J. 49:968-973.

42. Putnam, A. R. 1972. Efficacy of zero-tillage cultural system for asparagus produced from seed and crowns. J. Amer. Soc. Hort. Sci. 97(5):621-624.

43. Radke, J. K., A. R. Dexter, and 0. J. Devine. 1985. Tillage effects on soil temperature, soil water, and wheat growth in South Australia. Soil Sci. Soc. Am. J. 49:1542-1547.

44. Reicosky, D. C., D. K. Cassell, R. L. Blevins, W.R. Gill, and G. C. Naderman. 1977. Conservation tillage in the Southeast. J. of Soil and Water Conservation. 32(1):13-19.

45. Shear, G. M. and W. W. Moschler. 1969. Continuous com by the no- tillage and con-ventional tillage methods: a six-year comparison. Agron. J. 61:524-526.

46. Tessore, C., W. E. Chappell, R. D. Morse, and C.R. O'Dell. 1981. No-till fall vegetable experiments. The Veg. Growers News. 35(7):2-3.

47. Thornton, R. 1977. Minimum tillage - - for potatoes. Amer. Veg. Grower. 25(5):30-32.

LITERATURE CITED 13

48. Tompkins, F. D., B. L. Bledsoe, and C. A. Mullins. 1976. Minimum tillage snap beans. Tenn. Farm and Home Sci. 98:18-20.

49. Triplett, G. B., Jr. 1975. Fertilizer use for no-tillage systems. TV A Fert. Conf.:65-72.

50. Triplett, G. B., Jr. and G.D. Lytle. 1972. Control and ecology of weeds in continuous corn grown without tillage. Weed Sci. 20(5):453-457.

51. Triplett, G. B.,Jr., D. M. Van Doren, Jr. and B. L. Schmidt. 1968. Effect of corn (Zea mays L.) stover mulch on ~no-tillage corn yield and water infiltration. Agron J. 60:236-239.

52. Valiulis, D. 1983. Reduced tillage turns up soil fertility factors and needs. Agrichem. Age. Aug/Sept:48-50.

53. Williams, J. L., Jr. and G. A. Wicks. 1978. Weed control problems associated with crop residue systems. p. 165-172. In: W. J. Oschwald, ed. Crop Residue Management Sys-tems. ASA Spec. Pub. No. 31.

54. Wruke, M.A. and W. E. Arnold. 1985. Weed species distribution as influenced by tillage and herbicides. Weed Sci. 33:853-856.

LITERATURE CITED 14

MATERIALS AND METHODS

Experimental sites were located in Carroll County, Virginia, in 1985 on a Chester Glcnelg

loam soil (pH 6.3) and in 1986 on a Lodi silt loam (pH 6.4) at the Horticulture Research Farm

near Blacksburg, Virginia.

The experimental design both years was a split plot with planting dates as main plots ( 1985,

18.3 x 6.1 m; 1986, 14.6 x 4.9 m), and tillage systems as split plots (1985, 4.6 x 6.1 m; 1986, 3.7 x

4.9 m). Four replications of each planting date were used. Two guard rows and two harvest rows

were planted in each sub plot.

Sprillg, Summer 1985

Cereal rye ( Secale cereale L.) at 125 kg/ha was seeded in the fall of 1984 as a cover crop.

Glyphosate, N-phosphonomethyl glycene at 2.24 kg ai/ha was applied as a knock-down herbicide

to the entire field two weeks before the first planting date. The rye was 61-76 cm tall when

glyphosate was applied.

MATERIALS AND METHODS 15

Four tillage systems were used: 1) conventional tillage (CT), plowed and disked prior to

transplanting; 2) no-tillage (NT), plants set into undisturbed sod; 3) row-tillage, strip tilled with a

two row Bushhog Ro-Till (RT) machine with 91 cm row spacing (8, 13); and 4) chisel plow (CP),

strip chiseled using a locally constructed tool bar with two chisels spaced 91 cm apart ( 18). Al-

though RT and CP are types of strip tillage (ST), there is a distinct difference between them. In

the RT plots, a subsoiler shank at a depth of approximately 25 cm, a dual-coulter system and a

rolling basket were used to thoroughly till a strip 40 cm wide; while in CP a chisel shank opened

a narrow slit 20 cm deep leaving an untillcd narrow strip approximately 15-20 cm wide. A flat bed

free of clods and plant residues resulted from RT, while an uneven depression containing clods and

some plant residues occurred with the CP.

On May 29, tillage systems were established for all planting dates and napropramide, 2-(a

-naphthoxy)-N,N-diethylpropionamide, was applied at 1.7 kg ai/ha over the entire field. Bareroot

'Gourmet' cabbage plants (Brassica oleracea var. capitata L.) were set at a 91 cm between row and

23 cm in-row spacing with a locally modified two row no-till transplanter. The planter was

equipped with two fertilizer hoppers, one per row, that surface banded 1600 kg/ha of

10N-4.3P-8.3K approximately 4 cm to the side of the row at planting. A Diazinon, O,O-dicthyl

O-(2-isopropyl-6-methyl-4-pyrimidinyl) phosphorothioate, solution (0.3 g ai/litcr) was hand ap-

plied at an approximate rate of 200 ml/plant for control of cabbage root maggots. Immediately

following planting, all misplaced and missing plants were reset by hand to maximize plant survival

and stand uniformity. The second planting was done on July 2 with the same transplanting pro-

cedure.

Prior to planting, cover crop biomass estimates were determined by sampling two 61 x 61 cm

areas. Rye samples were dried at 70°C and weighed (Table 2). Soil moisture was determined from

the top 10 cm by the gravimetric method twice in each tillage treatment for each planting date (7).

Soil temperature at a depth of 10 cm was recorded weekly with soil thermocouples for all tillage

systems.

MATERIALS AND METHODS 16

Hand weeding was done as necessary and recommended pesticides were applied at regular

intervals to control insects and diseases. Plots were harvested twice for each planting date beginning

August 8 and September 22 and again two weeks later, respectively, for each planting date. Head

number was the number of mature heads per plot at harvest time and was used as an estimate of

plant stand because very few plants did not form heads. Total head weight was recorded and weight

included 3-4 wrapper leaves. Weight per head was obtained by dividing total head weight by total

number of heads.

Spring, Summer 1986

Cereal rye was seeded at a rate of 125 kg/ha in the fall of 1985. Prior to sowing rye, nitrogen

was applied at a rate of 34 kg/ha. Most of the cover crop had been lost by the second planting date

in 1985; therefore, to assure an adequate cover for each planting date in 1986, only the areas to be

planted were killed and tillage methods installed just prior to each planting date. The subsequent

areas to be planted were mowed and allowed to continue growing until the next planting date.

Tillage systems and transplanting were the same as m 1985. Paraquat,

l,l'-dimethyl-4,4'-bipyridinium ion, at 0.56 kg ai/ha was used as the knock down herbicide when

the rye was 61-76 cm tall and was applied one to two days before establishing tillage methods.

Tillage systems were established and a combination of oxyfluorfcn,

2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(triflouromethyl)benzene, at 0.35 kg ai/ha and I. 7 kg ai/ha

of napropamide were applied in the morning before planting. The first planting date spray included

0.8 kg ai/ha paraquat due to poor rye kill with the first application. Herbicides were inadvertently

applied before tillage treatments were established in the second planting date, necessitating hand

weeding particularly in the CT plots. Rates of oxyfluorfen and napropamide were the same as those

at the other planting dates.

MATERIALS AND METHODS 17

Table 2. Dry matter yield of rye cover crop (\IT /ha).

Table 2. Dry matter yield of rye cover crop (MT/ha).

Plantin,¥ d'lte 1985 1986

I 3.(Y 2.6l 2 3.0a 3 3.3a

z Sampling dates were: 1985: 1 = May 30; 1986: l =

y:'\Pril 21, 2 = May 23, 3 = June 24. 1985 biomass samples were done once - the entire c_over crop was sprayed with glyphosate at the same

._trme. "Mean separation by Duncan's multiple range test, 5% level.

\L\TERIALS A'>;I) \IETIIODS IX

Bareroot 'Market Prize' cabbage transplants were used for the first two planting dates and 'A

& C 5' was used for the third planting date. The transplanting rate of fertilizer and pest control

were the same as in 1985. A solution mixture of diazinon (0.3 g ai/liter) and 9N-l 9P-12K Peters

starter fertilizer (6 g/liter) was hand applied after transplanting at approximately 200 ml per plant.

After the cabbage plants were set, the plots were irrigated with 4 cm of water to aid plant estab-

lishment and incorporate the herbicides. Planting dates were April 24, June 4 and July 8. Once

over harvest dates were July 18, August 26 and September 29, respectively.

Soil moisture samples were taken in the plant row three times per planting date in each tillage

treatment at a depth of 10 cm using the gravimetric method (7). Soil temperature at a depth of 10

cm was measured weekly in the plant rows. Cover crop biomass was determined by sampling each

rep for each planting date using similar procedures as in 1985 (Table 2).

Five cm of irrigation water were applied to all plots on July 22 when the soil became ex-

tremely dry due to drought conditions.

Data were statistically analyzed by analysis of variance using the General Linear Models

procedure on SAS (23).

MATERIALS A;\;D METHODS 19

RESULTS AND DISCUSSION

YIELD AND YIELD COMPONENTS. Tillage systems significantly affected yield per hectare

(Table 3). In 1985, yields with CT equalled RT and CP, and were significantly higher than with

NT. In 1986, yield in RT plots was significantly higher than in CT and NT and not significantly

different than CP. Strip tillage appeared to be the best alternative tillage method because it com-

bines the benefits of tillage and a mulch cover to produce an excellent growing environment. In-

dividual effects of planting dates and tillage systems for yield and yield components are shown in

the appendix (Tables 6, 7, 8).

Average head size among tillage systems was significantly different both years (Table 3) and

was the major component responsible for yield differences. The correlation between head size and

yield was highly significant with r values of 0.56•++ and 0.89•++ for 1985 and 1986, respectively.

There were no significant differences in head number among tillage systems either year (Table

3). Head number can be considered the same as plant stand since, with rare exception, all plants

produced a marketable head. Resetting misplaced and missing plants resulted in final plant survival

(percentage final plant stand with once-over resetting) of over 88% both years (Table 3). Resetting

is a standard practice of Carroll County cabbage growers. Even though resetting compensated for

planting failures in these experiments, excessive resetting in commercial operations would be un-

RESULTS AND DISCUSSION 20

desirable because of increased labor costs. Although plant survival was statistically the same for

all tillage treatments, plant numbers tended to be slightly higher in RT plots both years

(Table 3). Under windy and/or dry conditions, plant survival would be favored in all three con-

servation systems, especially in RT where the tilled, friable soil would tend to enhance soil-root

contact and rapid root growth (12).

Planting effectiveness (percentage plant stand without resetting) was not recorded in these

experiments. However, the numbers and extent of improperly set plants were notably greater with

NT and somewhat greater with CP plots than in CT and RT soils. The amount of large clods and

plant residues were correspondingly higher in CP and NT plots. It is therefore believed that the

relatively impediment-free condition and improved friability of the CT and RT soils would result

in greater planting effectiveness than with NT and possibly CP.

The RT would appear to have distinct advantages over NT and CP for conservation tillage

cabbage production when wet soils are a potential problem. In this study, the plant beds were flat

with all tillage systems; however, raised beds can be established with the RT by a simple adjustment

of the dual coulters (12). Raised beds would provide a potential advantage for the RT in situations

such as early spring plantings and/or poorly drained soils where excess surface water might be a

problem.

SOIL MOISTURE. Except for the second planting in 1985, soil moisture tended to be higher

in conservation tillage plots than in CT (Table 4). In 1985, soil moisture and yield were not cor-

related (r = -. l 7ns). These data are inconsistent with the 1986 findings (r = .6Q+++) and the re-

ports of other researchers who have shown a strong positive relationship between yield and soil

moisture content (3, 11, 15, 16, 17). Morse et al. ( 16) found higher fall yields and a corresponding

higher soil moisture content with NT than with CT for four vegetables studied--cabbage, cucumber,

tomato and squash. Planting date effect on soil moisture content is shown in the appendix (Table

9).

In 1985, after early July soil moisture content was not significantly different between tillage

systems and did not affect head yield. Unusually heavy rains in July and August (Table 5) and the

RES UL TS A1'1D DISCUSSION 21

Table 3. Influence of tillage systems on head number, yield anti size of cabbage.

z Table 3. Influence of tillage systems on head number, yield and size of cabbage.

Tillage;_ Head nrf Yield Head size system Y (1000/ha) (MT/ha) (kg/head)

1985 1986 1985 1986 1985 1986

CT 4l.6i" 42.la 61.9a 59.6b 1.5a l.4b

r-;T 41.3a 41.6a 52.3b 62.5b 1.3b Uab

RT 43.la 43.3a 59.9ab 70.8a l.4ab 1.6a

CP 41.9a 40.8a 58. lab 64.7ab 1.4ab 1.6a

y:fhere were no significant interactions between planting dates and tillage systems. CT = Conventional tillage; NT = No-tillage; RT = Ro-till; CP = Chisel plow.

7he theoretical "perfect" plant population at 91 x 23 cm would be 47,778 plants/ha. 1":\1can separation within columns by Duncan's multiple range test, 5% level.

1u:su:rs ,\:'\I) DISCLSSIO:--; 22

small quantity of mulch remaining during the second planting resulted in equal soil moisture con-

tent between tillage systems after early July.

Although there were significant soil moisture differences recorded for the first planting (Table 4),

these data did not reflect subsequent yield differences because the soil moisture samples were taken

on June 13 and 25, which corresponded to the vegetative stage of plant development. During slow

development in the vegetative period, cabbage yield is little affected by water deficits. Once the head

formation stage is initiated, increases in weight of cabbage heads is nearly proportional to the

quantity of water applied ( 4, 5).

Although actual soil erosion data were not taken in this study, there was no evidence that

serious soil losses occurred in the plots either year. Heavy rainfall often results in serious soil ero-

sion in Carroll County (14) and other mountainous Appalachian regions, particularly when heavy

rains impact on freshly tilled soil. Probably no soil erosion problems occurred in our plots because

the research areas were relatively flat, and the heavy rains of 1985 occurred approximately two

months after tillage.

SOIL TEMPERATURE. Tillage systems did not significantly affect soil temperature either

year (Table 4). Many authors have reported lower soil temperatures under NT (1, 9, 10, 19, 21,

24). In our experiments, average soil temperature differences between treatments were less than one

0 c each year. Johnson and Lowery (10) reported lower soil temperatures under NT during the early

part of the growing season with differences lessening to less than one °C by the end of June. Radke

et al. (22) reported similar soil temperatures under NT and CT due to cool weather and rain.

Planting date effects on soil temperature are shown in the appendix (Table 9).

The thermocouple probes used for temperature readings in this study were located between

plants within the row. Apparently the disturbance and sloughing aside of plant residues by the

conservation planter removed enough in-row cover in the NT plots to minimize any in-row tem-

perature differences between tillage systems. Rapid decomposition of the rye cover prior to planting

in 1985 and dry weather during the first planting in 1986 probably contributed to the lack of tem-

perature differences. Beste (2) recorded higher temperatures under NT than under CT. He attri-

RES UL TS AND DISCUSSION 23

Table 4. · Effects of planting dates and tillage systems on soil temperature and soil moisture content

Table 4. Effects of planting dates and tillage systems on soil temperature and soil moisture content.

Planting Tillage system z

date CT l\T RT CP

Soil moisture ( % ) Y 1985

May 30 X 18.3c 28.4a 26.9ab 24.8b July 2 20.6a 20.9a 21.0a 20.6a Mean 19.Sc 24.4a 23.9ab 22.7b

1986

Apr 24 12.Sb 15.3a 13.3b 14.0ab June 4 15.0a 16.7a 16.7a 16.8a July 8 14.7a 15.7a 16.6a 16.7a Mean 14.lb 15.9a 15.Sa 15.8a

Soil temperature ( C) 1985

May 30 19.4a 19.7a 19.Sa 20.la July 2 23.0a 22.2a 22.8a 22.6a Mean 21.la 20.8a 21.0a 21.2a

1986

Apr 24 20.0a 19.6a 19.6a 19.Sa June 4 22.2a 21.9a 22.2a 21.9a July 8 20.7a 20.9a 20.7a 20.6a Mean 21.0a 20.9a 20.9a 20.7a

; CT = Conventional tillage; NT = No-tillage; RT = Ro-till; CP = Chisel Plow. There was a significant planting date x tillage systems moisture interaction in 1985; however, no moisture interaction occurred in 1986 or temperature interactions either year.

x Mean separation within rows Duncan's multiple range test, 5% level.

RESLLTS ,\:\D l)ISCLSSIO:'\ 24

Table 5. '.\1onthly and annual precipitation.

Table 5. Monthly and annual precipitation.

Carroll Co. Blacksburg

Month 1985 Average 1986 Average

-----------------mm-----------------Jan 76.2 69.l 29.2 74.9 Feb 90.7 77.5 92.2 74.7 Mar 54.l 88.6 49.5 99.3 Apr 52.3 83.8 37.6 90.2 May 152.4 90.4 168.9 91.9 June 63.2 100.6 32.5 91.7 July 162.8 115.8 99.8 92.7 Aug 249.2 102.l 84.l 89.7 Sept 14.2 97.8 95.5 88.4 Oct 62.7 77.5 62.2 79.8 Nov 231.4 70.4 68.l Dec 28.7 79.8 74.2

Total 1237.9 1053.4 751.5 1015.6

RF,St;LTS A'.';D DISCUSSION 25

buted the higher temperatures to reduced radiation losses of heat and by minimizing the cooling

effect of the wind with the straw mulch. This could have also been the situation in these plots.

PLANTING DATES X TILLAGE SYSTEMS INTERACTIONS. Lack of significant yield

interactions between planting dates and tillage systems indicates that differences in response of

growth determinants such as soil moisture and temperature to tillage systems were similar for all

planting dates. In early spring, lower temperatures and wet soils often occur with NT (I, 9, 10, 20).

Planting dated X tillage systems interactions frequently occur under cool, wet spring conditions

followed by increasing soil moisture deficits as the season progresses (6).

Although significant planting dates X tillage interactions did not occur either year, yield re-

sponse to tillage varied considerably over the two years and showed a strong relationship with

monthly rainfall patterns. In 1985, unusually heavy rainfall in July and August resulted in uniform

soil moisture between tillage systems (Table 5). The higher CT yields in 1985, compared to NT,

are attributed to observed improvements in soil root contact in tilled plots. In 1986, dry weather

occurred during plant establishment and early growth of the first planting, followed by a relatively

irregular rainfall pattern throughout the growing season (Table 5). As a result, soil moisture content

was consistently higher in NT than CT the entire year (Table 4). The similar yields between NT

and CT in 1986 (Table 3) are attributed to counterbalancing effects of higher soil moisture with

NT versus improved soil root contact with CT.

If cabbage were planted with NT under cool, wet conditions, poor root-soil contact at

planting and slow early plant growth would probably occur resulting in reduced yields ( 12). The

yield difference between tillage treatments and NT in early plantings probably would be greater

under high rainfall or when irrigation is applied throughout the growing season. Ample moisture

supplies, especially during the rapid head development stage when cabbage requires abundant

moisture (5, 6) would tend to offset any potential advantages of NT over the other tillage treatments

in conserving soil moisture.

RES UL TS AND DISCUSSION 26

CONCLUSIONS

l. All conservation tillage systems performed well under the conditions of this study.

2. In 1985, when soil moisture was not limiting, CT outyielded NT probably because of observed improvements in soil- root contact with CT. Under the intennittent deficit soil moisture conditions found in 1986, conservation of soil moisture by the plant residues resulted in improved NT yields, equalling those with CT.

3. Yields with strip tillage (RT and CP) equalled or were higher than with NT or CT both years. Strip tillage appeared to be the best overall tillage choice under either ample or deficit soil moisture. The combination of in-row tillage for improved planting efficiency and soil physical condition and between-row cover for moisture and soil conservation make strip tillage an excellent compromise between NT and CT.

4. In situations where soil erosion is a major concern, NT would probably be the preferred tillage treatment over strip tillage, unless the grower paid strict attention to proper con-tour planting procedures. Because of the relatively small fields and irregular terrain in mountainous Appalachia, contour farming is not a well established practice. Studies arc needed to evaluate the effects of different strip tillage systems on soil erosion.

5. Planting dates X tillage yield interactions did not occur either year. Abnormally heavy summer rainfall in 1985 and dry spring weather in 1986 probably accounted in large measure for the lack of yield interactions.

CONCLUSIONS 27

LITERATURE CITED

1. Bennett, 0. L., E. L. Mathias, and P. E. Lundberg. 1973. Crop responses to no-tillage management practices on hilly terrain. Agron. J. 65:488-491.

2. Beste, C. E. 1973. Evaluation of herbicides in no-till planted cucumbers, tomatoes, and lima beans. NE Weed Sci. Soc. Proc. 27:232-239.

3. Blevins, R. L., D. Cook, S. H. Phillips, and R. E. Phillips. 1971. Influence of no-tillage on soil moisture. Agron. J. 63:593-596.

4. Doorenbos, J. and A. H. Kassam. 1979. Yield response to water. p.80-82. FAO Irri-gation and Drainage Paper, No. 33. Rome.

5. Drew, D. H. 1966. Irrigation studies on summer cabbage. J. Hort. Sci. 41:103-114.

6. Eckert, D. J. 1984. Tillage system x planting date interactions in com production. Agron. J. 76:580-582.

7. Gardener, W. H. 1965. Water Content. p. 92-96. In C. A. Black (ed.). Methods of soil analysis. Part I. Amer. Soc. Agron., Madison, WI.

8. Gergen, B. 1981. One-pass tillage tool. Farm Ind. News. May-June 198 l :60.

9. Griffith, D. R., J. V. Mannering, H. M. Galloway, S. D. Parsons, and C. n. Richey. 1973. Effect of eight tillage-planting systems on soil temperature, percent stand, plant growth, and yield of com on five Indiana soils. Agron. J. 65:321-326.

10. Johnson, M. D. and B. Lowery. 1985. Effect of three conservation tillage practices on soil temperature and thermal properties. Soil Sci. Soc. Am. J. 49: 1547-1552.

1 l. Jones, J. N., Jr., J.E. Moody, and J. H. Lillard. 1969. Effects of tillage, no-tillage, and mulch on soil water and plant growth. Agron. J. 61:719-722.

12. Knavel, D. E. and J. W. Herron. 1981. Influence of tillage system, plant spacing, and nitrogen on head weight, yield, and nutrient concentration of spring cabbage. J. Amer. Soc. Hort. Sci. 106(5)540-545.

13. Konsler, T. R. and G. D. Hoyt. 1986. Response of broccoli and cabbage to winter cover residues and degree of tillage. (Unpub. data).

14. McGrady, H. 1983. Chairman, New River Soil and Water Conservation District. Per-sonal Correspondence.

LITERATURE CITED 28

15. Morse, R., B. McMaster, and C. Tessore. 1983. Increased squash yields with no-tillage mulch. The Veg. Growers News. 37(5):1.

16. Morse, R. D. and C. Tessore. 1984. Efficient water use: conservation of soil moisture with no-tillage. The Veg. Growers News. 39(3):1&4.

17. Morse, R. D., C. M. Tessore, W. E. Chappell, and C. R. O'Dell. 1982. Use of no-tillage for summer vegetable production. The Veg. Growers News. 37(1): I.

18. Oschwald, W. R. 1973. Chisel plow and strip tillage systems. p.194-202. In: Soil Cons. Soc. Amer. Conservation tillage: the proceedings of a national conference. Ankeny, Iowa.

19. Peterson, C. L., E. A. Dowding, K. N. Hawley, and R. W. Harden. 1983. The chisel-planter minimum tillage system. Trans. of ASAE.:378-383.

20. Peterson, K. L., H.J. Mack, and D. E. Booster. 1986. Effect of tillage on sweet corn development and yield. J. Amer. Soc. Hort. Sci. 111(1):39-42.

21. Potter, K. N., R. M. Cruse, and R. Horton. 1985. Division S-6-soil and water man-agement and conservation: tillage effects on soil thermal properties. Soil Sci. Soc. Am. J. 49:968-973.

22. Radke, J. K., A. R. Dexter, and 0. J. Devine. 1985. Tillage effects on soil temperature, soil water, and wheat growth in South Australia. Soil Sci. Soc. Am. J. 49:1542-1547.

23. SAS Institute. 1985. SAS User's Guide: Statistics, Version 5. SAS Institute, Cary, NC.

24. Tessore, C., W. E. Chappell, R. D. Morse, and C. R. O'Dell. 1981. No-tillage fall veg-etable experiments. The Veg. Growers News. 35(7):2-3.

LITERATURE CITED 29

APPENDIX

APPENDIX 30

Table 6. Individual effects of planting date and tillage system on head number, yield and size of cabbage in 1985.

Table 6. Individual effects of planting date and tillage system on head number, yield and size of cabbage in 1985.

Tillage systcrrf

CT NT RT CP

CT NT RT CP

CT NT RT CP

May 30

41,9/ 38.3a 44.4a 40.6a

63.8a 51.2a 63.6a 58.3a

!.Sa 1.3a 1.4a 1.4a

Planting date

Head no (1000/ha)

Yield (MT/ha)

Head size (kg/head)

July 2

41.3a 44.2a 41.7a 43.3a

60.la 53.3a 56.3a 58.0a

1.5a 1.2b l.3ab l.3ab

z CT = Conventional tillage; NT = No-tillage; RT = Ro-till; CP = Chisel plow. Y Mean separation within column by Duncan's multiple range test, 5% level.

Al'l'E:\'DIX JI

Table 7. Individual e_ffects of planting dates and tillage systems on head number, yield and head size of cabbage m 1986.

Table 7. Individual effects of planting dates and tillage systems on head number, yield, and head size of cabbage in 1986.

Tillagez Planting date system Apr 24 June 4 July 8

Head no (1000/ha)

CT V 41. lrt 42.6a 42.3a NT 41.8a 42.6a 40.0a RT 43.4a 43.2a 43.4a CP 41.5a 40.4a 40.6a

Yield (MT/ha)

CT 50.la 57.4b 69.0b NT 54.0a 65.4ab 67.2b RT 55.4a 75.0a 82.0a CP 53.0a 67.4ab 70.Sab

Head size (kg/head)

CT 1.2a 1.4b 1.6a NT 1.3a l.5ab 1.7a RT 1.3a 1.8a 1.9a CP 1.3a 1.7a 1.7a

J:T = Conventional tillage; NT = No-tillage; RT = Ro-till; CP = Chisel plow. 'Mean separation within column by Duncan's multiple range test, 5% level.

Al'l'E:\'DIX J2

Table 8. Influence or planting date on head number, size and yield or cabbage.

Table 8. Influence of planting date on head number, size and yield of cabbage.z

Plantin,$ date Y

Head no Yield Head size (1000/ha) (MT/ha) (kg/head)

2

3

1985

41.3ax

42.6a

1986

42.0a

42.2a

41.7a

1985 1986 1985

59.2a 53.3b 1.4a

56.9a 66.3ab 1.3a

---- 72.6a

9There were no significant interactions between planting dates and tillage systems. 1985: 1 = May 30, 2 = July 2; 1986: 1 = April 24, 2 = June 4, 3 = July 8.

XMean separation within columns by Duncan's Multiple range test, 5% level.

Al'l'E:'\DIX

1986

1.3b

1.6ab

1.7a

JJ

Table 9. Influence of planting dates on soil moisture and soil temperature.

Table 9. Influence of planting dates on soil moisture and soil temperature.

Planting date2

1 2 3

Soil moisture ( % )

1985 1986

y 13.8b x 16.3a 15.9a

Soil temperature fC) 1985 1986

19.7b 22.7,

19.7c 22.0a 20.7b

~985: 1 = May 30, 2 = July 2; 1986: l = April 24, 2 = June 4, 3 = July 8. There was a significant soil moisture interaction between planting dates and tillage sys-

Jems in 1985; see Table 3. "Mean separation within columns for each main effect by Duncan's multiple range test, 5% level.

"Only two plantings were established in 1985.

Al'l'E:'\DIX

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